1. Field of the Invention
The present invention relates to an apparatus for fixing to and removing from an arbor an annular cutter for forming at least one relatively deep hole in a workpiece made of a hard material such as steel, and more particularly to an apparatus for fixing an annular cutter to an arbor easily in one touch operation.
2. Description of the Related Art As known well, a drilling machine for drilling workpieces made of a hard material generally rotates and feeds, at a constant speed, an annular cutter provided with on its lower circular edge with cutting blades for forming a hole or holes in each workpiece. Before new drilling operation is performed with a drilling machine, the annular cutter now on the machine must be replaced by new one which has the same outer diameter as the inner diameter of holes to be formed in the workpiece. For easy replacement of the annular cutter, there have been developed various apparatuses for fixing an annular cutter to or detaching the same from an arbor.
A typical example of such a conventional apparatus for fixing an annular cutter to and detaching the same from an arbor is disclosed in Japanese Laid-open Patent Application No. 62-74515.
In this conventional annular-cutter fixing apparatus, a rotation transmitting member is inserted in the axial bore formed in the lower end portion of an arbor and is fixed to the arbor by a key. An operation sleeve urged downward by a first spring is axially slidably mounted on the lower end portion of the rotation transmitting member. An annular engaging portion is formed in the lower end portion of the operation sleeve and urged downward by a second spring so that the annular engaging portion inwardly presses balls in engaging holes radially extending through the rotation transmitting member in such a manner that a part of each ball projects inward from the inner wall of the rotation transmitting member.
The ways how to fix an annular cutter to and detach the same from the arbor in this conventional apparatus will be explained.
The operation sleeve is lifted against the first spring and the annular engaging portion is displaced away from the outer opening of the engaging holes to make the balls free. Next, the shank of an annular cutter is inserted into the axial bore of the rotation transmitting member from its lower end. The outer wall of the shank presses the balls into the engaging holes, and the shank is continued to be inserted into the rotation transmitting member until an annular engaging groove formed in the outer wall of the shank aligns with the inner opening of the engaging holes. When the operation sleeve is released in this state and lowered, the annular engaging portion engages the balls and pushes them inward, and the balls engage the annular engaging grooves in the shank, whereby the annular cutter is fixed to the arbor.
On the other hand, the operation sleeve is lifted against the second spring with an annular cutter fixed to the arbor, and the annular engaging portion is displaced from the outer opening of the engaging holes so that the balls are made free again in the engaging holes. Then, the shank of the annular cutter is pulled off the rotation transmitting member. Thereafter, the operation sleeve is released to be returned to the normal position. In doing so, the arbor is removed from the operation cutter.
When, however, the annular cutter is fixed to the drilling machine which is provided with the conventional annular cutter fixing apparatus, the operation sleeve is pushed against the second spring with one hand of the operator, and, at the same time, the shank of the annular cutter is inserted into the rotation transmitting member by the other hand. The operator must use both hands in order to fix the annular cutter to the arbor. Thus, the cutter cannot be fixed to drilling machine in one touch operation with a single hand in a simple way without accompanying rotation of the annular cutter.